This invention relates in general to thrust washers that are disposed between the outer ends of trunnions and the inner surfaces of bearing cups in universal joint assemblies. More specifically, this invention relates to an improved structure for such a thrust washer that is formed having a protrusion that extends within a portion of a passageway formed in the outer end of the trunnion for positively positioning the thrust washer relative to the trunnion during use.
Universal joints are well known devices that provide a driving connection between two members adapted to rotate about non-aligned axes of rotation. Universal joints are widely used between rotatable drive shaft sections in vehicle drive train systems. A typical universal joint includes a cross having a central body portion with four cylindrical trunnions extending outwardly therefrom. The trunnions are oriented in a single plane and extend at right angles relative to one another. A hollow cylindrical bearing cup having a cylindrical outside wall and a circular end wall is mounted on the end of each of the trunnions. A plurality of bearings, such as needle bearings or roller bearings, are provided between the trunnion and the associated bearing cup to permit relative rotational movement therebetween. The bearing cups that are mounted on a first opposed pair of the trunnions can be connected to a first end yoke secured to an end of a first drive shaft section, while the bearing cups mounted on a second opposed pair of the trunnions can be connected to a second end yoke secured to an end of a second drive shaft section.
When the bearing cups are mounted on the opposed pair of trunnions, the end walls of the bearing cups are disposed adjacent to the axially outer ends of the trunnions and bearings. If the end walls of the bearing cups are fit tightly against the axially outer ends of the trunnions and bearings, friction between the surfaces during operation of the universal joint can generate heat and cause premature wear. If the bearing cups are fit loosely on the trunnions, the cross and trunnions can move back and forth within the opposed bearing cups during operation of the universal joint. This may create imbalance of the universal joint and generate undesirable noise and vibrations. To address these situations, it is known to position thrust washers between the end walls of the bearing cups and the axially outer ends of the trunnions and bearings. A typical thrust washer is formed from a wear-resistant material, such as plastic, that can absorb the thrust loads that occur between the ends of the trunnions and the bearing caps and take up any looseness therebetween.
To insure optimal function, it is desirable that the thrust washer be installed in a centered positioned relative to the outer end of the trunnion upon which it is located. Furthermore, it is desirable that such thrust washer be maintained in that centered position during subsequent use. Unfortunately, it has been found that the initial positioning of the thrust washer in a centered position on the outer end of the trunnion can add undesirable time and effort to the assembly process for the universal joint. Also, it is known that a conventional thrust washers can move laterally relative to the outer end of the trunnion upon which it is located during use. Thus, it would be desirable to provide an improved structure for a thrust washer that can facilitate the installation thereof in a centered position on the outer end of the trunnion and subsequently maintain the thrust washer in that desired position during use.